Vishnu after performing tapas on krishna for 100 manvantara's
became protector.Similarly all the devatas become eligible for puja
after doing tapas on krishna.
vyakhya - It seems wonder that even vishnu after performing tapas
on krishna becomes protector.There is an instance in this puraana
that vishnu was asking krishna for his service and by the vara pradaan
of krishna he became amara dev(immortal) like krishna .

So by now all of you have understood that krishna is the isvara of
all devatas even for siva and vishnu